package cn.newtouch.util.web;

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.Map.Entry;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang3.Validate;

import cn.newtouch.util.utils.Encodes;

import com.google.common.net.HttpHeaders;

/**
 * Http与Servlet工具类.
 * 
 * @author calvin
 */
public class Servlets
{

    // -- 常用数值定义 --//
    public static final long ONE_YEAR_SECONDS = 60 * 60 * 24 * 365;

    /**
     * 设置客户端缓存过期时间 的Header.
     */
    public static void setExpiresHeader(HttpServletResponse response,
            long expiresSeconds)
    {
        // Http 1.0 header, set a fix expires date.
        response.setDateHeader(HttpHeaders.EXPIRES, System.currentTimeMillis()
                + expiresSeconds * 1000);
        // Http 1.1 header, set a time after now.
        response.setHeader(HttpHeaders.CACHE_CONTROL, "private, max-age="
                + expiresSeconds);
    }

    /**
     * 设置禁止客户端缓存的Header.
     */
    public static void setNoCacheHeader(HttpServletResponse response)
    {
        // Http 1.0 header
        response.setDateHeader(HttpHeaders.EXPIRES, 1L);
        response.addHeader(HttpHeaders.PRAGMA, "no-cache");
        // Http 1.1 header
        response.setHeader(HttpHeaders.CACHE_CONTROL,
                "no-cache, no-store, max-age=0");
    }

    /**
     * 设置LastModified Header.
     */
    public static void setLastModifiedHeader(HttpServletResponse response,
            long lastModifiedDate)
    {
        response.setDateHeader(HttpHeaders.LAST_MODIFIED, lastModifiedDate);
    }

    /**
     * 设置Etag Header.
     */
    public static void setEtag(HttpServletResponse response, String etag)
    {
        response.setHeader(HttpHeaders.ETAG, etag);
    }

    /**
     * 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
     * 
     * 如果无修改, checkIfModify返回false ,设置304 not modify status.
     * 
     * @param lastModified
     *            内容的最后修改时间.
     */
    public static boolean checkIfModifiedSince(HttpServletRequest request,
            HttpServletResponse response, long lastModified)
    {
        long ifModifiedSince = request
                .getDateHeader(HttpHeaders.IF_MODIFIED_SINCE);
        if ((ifModifiedSince != -1) && (lastModified < ifModifiedSince + 1000))
        {
            response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
            return false;
        }
        return true;
    }

    /**
     * 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
     * 
     * 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
     * 
     * @param etag
     *            内容的ETag.
     */
    public static boolean checkIfNoneMatchEtag(HttpServletRequest request,
            HttpServletResponse response, String etag)
    {
        String headerValue = request.getHeader(HttpHeaders.IF_NONE_MATCH);
        if (headerValue != null)
        {
            boolean conditionSatisfied = false;
            if (!"*".equals(headerValue))
            {
                StringTokenizer commaTokenizer = new StringTokenizer(
                        headerValue, ",");

                while (!conditionSatisfied && commaTokenizer.hasMoreTokens())
                {
                    String currentToken = commaTokenizer.nextToken();
                    if (currentToken.trim().equals(etag))
                    {
                        conditionSatisfied = true;
                    }
                }
            }
            else
            {
                conditionSatisfied = true;
            }

            if (conditionSatisfied)
            {
                response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                response.setHeader(HttpHeaders.ETAG, etag);
                return false;
            }
        }
        return true;
    }

    /**
     * 设置让浏览器弹出下载对话框的Header.
     * 
     * @param fileName
     *            下载后的文件名.
     */
    public static void setFileDownloadHeader(HttpServletResponse response,
            String fileName)
    {
        try
        {
            // 中文文件名支持
            String encodedfileName = new String(fileName.getBytes(),
                    "ISO8859-1");
            response.setHeader(HttpHeaders.CONTENT_DISPOSITION,
                    "attachment; filename=\"" + encodedfileName + "\"");
        }
        catch (UnsupportedEncodingException e)
        {
        }
    }

    /**
     * 取得带相同前缀的Request Parameters, copy from spring WebUtils.
     * 
     * 返回的结果的Parameter名已去除前缀.
     */
    public static Map<String, Object> getParametersStartingWith(
            ServletRequest request, String prefix)
    {
        Validate.notNull(request, "Request must not be null");
        Enumeration paramNames = request.getParameterNames();
        Map<String, Object> params = new TreeMap<String, Object>();
        if (prefix == null)
        {
            prefix = "";
        }
        while (paramNames != null && paramNames.hasMoreElements())
        {
            String paramName = (String) paramNames.nextElement();
            if ("".equals(prefix) || paramName.startsWith(prefix))
            {
                String unprefixed = paramName.substring(prefix.length());
                String[] values = request.getParameterValues(paramName);
                if (values == null || values.length == 0)
                {
                    // Do nothing, no values found at all.
                }
                else
                    if (values.length > 1)
                    {
                        params.put(unprefixed, values);
                    }
                    else
                    {
                        params.put(unprefixed, values[0]);
                    }
            }
        }
        return params;
    }

    /**
     * 组合Parameters生成Query String的Parameter部分, 并在paramter name上加上prefix.
     * 
     * @see #getParametersStartingWith
     */
    public static String encodeParameterStringWithPrefix(
            Map<String, Object> params, String prefix)
    {
        if (params == null || params.size() == 0)
        {
            return "";
        }

        if (prefix == null)
        {
            prefix = "";
        }

        StringBuilder queryStringBuilder = new StringBuilder();
        Iterator<Entry<String, Object>> it = params.entrySet().iterator();
        while (it.hasNext())
        {
            Entry<String, Object> entry = it.next();
            queryStringBuilder.append(prefix).append(entry.getKey())
                    .append('=').append(entry.getValue());
            if (it.hasNext())
            {
                queryStringBuilder.append('&');
            }
        }
        return queryStringBuilder.toString();
    }

    /**
     * 客户端对Http Basic验证的 Header进行编码.
     */
    public static String encodeHttpBasic(String userName, String password)
    {
        String encode = userName + ":" + password;
        return "Basic " + Encodes.encodeBase64(encode.getBytes());
    }
}
